A suggestion, which might be unworkable... track in some way when questions are found in search engines or SE search. For external search engines I suppose you can only track when someone comes to the question from the search-results page?

My thinking is this would reward questions which are titled in a search-friendly way.

We should reward people for simply viewing a number of questions displayed in a search - even if it's only from the possible duplicate title list for a new question and the search field on SO pages. I'd like to see a small reputation bonus but a badge might work, too.

This would work like the bonus/badge you get for reviewing the FAQ. Just getting some users used to looking at possible dups via search would have an overall positive effect of the number of actual dup questions asked.

I think 10 rep and a badge might not sound like much to us, but to someone just starting out on SO it might be enough to get them in the habit of searching more.